Source Spectral studies using Lg wave in western Tibet

2020 ◽  
Author(s):  
Sukanta Sarkar ◽  
Namrata Jaiswal ◽  
Chandrani Singh ◽  
Arun Kumar Dubey ◽  
Arun Singh
Keyword(s):  
Spectral Characteristics ◽  
Corner Frequency ◽  
Spectral Studies ◽  
Local Magnitude ◽  
Tectonic Structure ◽  
Study Region ◽  
Karakoram Fault ◽  
Lg Wave ◽  
Tectonic Settings ◽  
The Moment

<p>The tectonic structure of western Tibet is complex and formed of several blocks, which are separated by distinct suture zones. This complexity makes the region very crucial for understanding the local tectonic settings. Here, we investigate the spectral characteristics of <em>Lg</em> wave from 420 waveforms recorded at 26 seismic stations located across Karakoram Fault (KKF) in western Tibet. We subdivide the study region into two parts across KKF. A frequency  dependent <em>Q<sub>Lg</sub></em> is observed in both sides of KKF with strong attenuation in the crust. The moment magnitude of each earthquake is computed using displacement spectra and subsequently compared with the reported local magnitude. Variations of the corner frequency with magnitude and distance<br>are also studied, which show a decreasing nature due to the path dependency.</p>

scholarly journals Analysis of strong-motion data of the 1990 Eastern Sicily earthquake

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
M. Di Bona ◽  
M. Cocco ◽  
A. Rovelli ◽  
R. Berardi ◽  
E. Boschi
Keyword(s):  
Frequency Band ◽  
Stress Drop ◽  
Seismic Moment ◽  
Ground Motions ◽  
Broad Band ◽  
Strong Motion ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Local Magnitude ◽  
The Moment

The strong motion accelerograms recorded during the 1990 Eastern Sicily earthquake have been analyzed to investigate source and attenuation parameters. Peak ground motions (peak acceleration, velocity and displacement) overestimate the values predicted by the empirical scaling law proposed for other Italian earthquakes, suggesting that local site response and propagation path effects play an important role in interpreting the observed time histories. The local magnitude, computed from the strong motion accelerograms by synthesizing the Wood-Anderson response, is ML = 5.9, that is sensibly larger than the local magnitude estimated at regional distances from broad-band seismograms (ML = 5.4). The standard omega-square source spectral model seems to be inadequate to describe the observed spectra over the entire frequency band from 0.2 to 20 Hz. The seismic moment estimated from the strong motion accelerogram recorded at the closest rock site (Sortino) is Mo = 0.8 x 1024 dyne.cm, that is roughly 4.5 times lower than the value estimated at regional distances (Mo = 3.7 x 1024 dyne.cm) from broad-band seismograms. The corner frequency estimated from the accelera- tion spectra i.5 J; = 1.3 Hz, that is close to the inverse of the dUl.ation of displacement pulses at the two closest recording sites. This value of corner tì.equency and the two values of seismic moment yield a Brune stress drop larger than 500 bars. However, a corner frequency value off; = 0.6 Hz and the seismic moment resulting from regional data allows the acceleration spectra to be reproduced on the entire available frequency band yielding to a Brune stress drop of 210 bars. The ambiguity on the corner frequency value associated to this earthquake is due to the limited frequency bandwidth available on the strong motion recordil1gs. Assuming the seismic moment estimated at regional distances from broad-band data, the moment magnitude for this earthquake is 5.7. The higher local magnitude (5.9) compared with the moment magnitude (5.7) is due to the weak regional attenuation. Beside this, site amplifications due to surface geology have produced the highest peak ground motions among those observed at the strong motion sites.

Calculation of Spectrum Characteristics for Braking Modes of Linear Induction Motors

2010 ◽  
Vol 164 ◽  
pp. 41-46 ◽  
Author(s):  
Bronius Karaliunas ◽  
Edvardas Matkevicius
Keyword(s):  
Magnetic Field ◽  
Continuous Spectrum ◽  
Spectral Characteristics ◽  
Positive Sequence ◽  
Linear Induction ◽  
Linear Induction Motor ◽  
Sequence Components ◽  
The Moment ◽  
Main Component ◽  
Analytical Expressions

The purpose of the wok is to derive analytical expressions of spectral characteristics at electrical braking of linear induction motor with diverse number of poles as well as to provide results of calculations. The major task in the analysis of braking modes is to determine spectral characteristics of braking current, primary magnetic field and braking force. To this aim Maxwell equations were solved together with Fourier and Laplace integral transformations. The obtained results indicate that in addition to the main component of the magnetic field, when the space frequency is , in the process of braking there appears continuous spectrum of elementary components with the frequencies occupying the infinite sector from - to + . Due to that fact, during the process of energy conversion at the moment of braking, there participate positive – sequence, negative – sequence components and elementary components of the continuous spectrum, motionless in the space.

scholarly journals Spectroscopic Evolution of Nova Vul 1984 No. 1 (PW Vul) and No. 2

1987 ◽  
Vol 93 ◽  
pp. 157-165
Author(s):  
L. Rosino ◽  
T. Iijima
Keyword(s):  
Spectral Characteristics ◽  
Spectroscopic Observations ◽  
The Moment ◽  
Preliminary Description

AbstractSpectroscopic observations of two novae (Nova Vul 1984 No. 1 and No. 2) have been carried out at the Asiago Observatory from the moment of their discovery up to now. A short preliminary description of the spectral characteristics and evolution of these two novae is reported together with a brief comparison of their properties.

scholarly journals Temporal Evolutions of N2+ Meinel (1,2) Band Near 1.5 μm Associated with Aurora Breakup and their Effects on Mesopause Temperature Estimations from OH Meinel (3,1) Band

2020 ◽  
Author(s):  
Takanori Nishiyama ◽  
Makoto Taguchi ◽  
Hidehiko Suzuki ◽  
Peter Dalin ◽  
Yasunobu Ogawa ◽  
...  
Keyword(s):  
Near Infrared ◽  
Rotational Temperature ◽  
Spectral Characteristics ◽  
Ratio Method ◽  
Line Pair ◽  
Syowa Station ◽  
Brightness Coefficient ◽  
Imaging Observation ◽  
The Moment ◽  
Mesopause Temperature

Abstract We have carried out ground-based NIRAS (Near-InfraRed Aurora and airglow Spectrograph) observations at Syowa station, Antarctic (69.0°S, 39.6°E) and Kiruna (67.8°N, 20.4°E), Sweden for continuous measurements of hydroxyl (OH) rotational temperatures and a precise evaluation of aurora contaminations to OH Meinel (3,1) band. A total of 368-nights observations succeeded for two winter seasons, and three cases in which N+2 Meinel (1,2) band around 1.5 μm was significant were identified. Focusing on two specific cases, detailed spectral characteristics with high temporal resolutions of 30 seconds are presented. Intensities of N+2 band were estimated to be 228 kR and 217 kR just at the moment of the aurora breakup and arc intensifications during pseudo breakup, respectively. At a wavelength of P1(2) line (∼ 1523 nm), N+2 emissions were almost equal to or greater than the OH line intensity. On the other hand, at a wavelength of P1(4) line (∼ 1542 nm), the OH line was not seriously contaminated and still dominant to N+2 emissions. Furthermore, we evaluated N+2 (1,2) band effects on OH rotational temperature estimations quantitatively for the first time. Aurora contaminations from N+2 (1,2) band basically lead negative bias in OH rotational temperature estimated by line-pair-ratio method with P1(2) and P1(4) lines in OH (3,1) band. They possibly cause underestimations of OH rotational temperatures up to 40 K. In addition, N+2 (1,2) band contaminations were temporally limited to a moment around aurora breakup. This is consistent with proceeding studies reporting that enhancements of N+2 (1,2) band were observed associated with International Brightness Coefficient 2-3 auroras. It is also suggested that the contaminations would be neglected in polar cap and sub-aurora zone, where strong aurora intensifications are less observed. Further spectroscopic investigations at this wavelength are needed especially for more precise evaluations of to N+2 (1,2) band contaminations. For example, simultaneous 2-D imaging observation and spectroscopic measurement with high spectral resolutions for airglow in OH (3,1) band will make great advances in more robust temperature estimations.

scholarly journals Study of recent outburst in the Be/X-ray binary RX J0209.6−7427 with AstroSat: a new ultraluminous X-ray pulsar in the Magellanic Bridge?

2020 ◽  
Vol 495 (3) ◽  
pp. 2664-2672 ◽  
Author(s):  
Amar Deo Chandra ◽  
Jayashree Roy ◽  
P C Agrawal ◽  
Manojendu Choudhury
Keyword(s):  
Energy Band ◽  
Spectral Characteristics ◽  
Spectral Studies ◽  
X Rays ◽  
Energy Bands ◽  
Large Area ◽  
Pulse Profile ◽  
X Ray ◽  
Outburst Energy ◽  
Area X

ABSTRACT We present the timing and spectral studies of RX J0209.6–7427 during its rare 2019 outburst using observations with the Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC) instruments on the AstroSat satellite. Pulsations having a periodicity of 9.29 s were detected for the first time by the NICER mission in the 0.2–10 keV energy band and, as reported here, by AstroSat over a broad energy band covering 0.3–80 keV. The pulsar exhibits a rapid spin-up during the outburst. Energy resolved folded pulse profiles are generated in several energy bands in 3–80 keV. To the best of our knowledge this is the first report of the timing and spectral characteristics of this Be binary pulsar in hard X-rays. There is suggestion of evolution of the pulse profile with energy. The energy spectrum of the pulsar is determined and from the best-fitting spectral values, the X-ray luminosity of RX J0209.6−7427 is inferred to be 1.6 × 1039 erg s−1. Our timing and spectral studies suggest that this source has features of an ultraluminous X-ray pulsar in the Magellanic Bridge. Details of the results are presented and discussed in terms of the current ideas.

Complexities of underground mining seismic sources

2021 ◽  
Vol 379 (2196) ◽  
pp. 20200134 ◽  
Author(s):  
Lindsay M. Linzer ◽  
Mark W. Hildyard ◽  
Johan Wesseloo
Keyword(s):  
Underground Mining ◽  
Moment Tensor ◽  
Source Parameters ◽  
Corner Frequency ◽  
Seismic Sources ◽  
Fracture Dynamics ◽  
Robust Parameter ◽  
Frequency Source ◽  
The Moment ◽  
Seismic Magnitude

This paper presents a numerical investigation on the influence of the mining environment on seismic sources, with a focus on pillar failure mechanisms in tabular mining. We investigate the influence of the mining stope (underground excavation or void) on seismic inversions for the scalar moment, corner frequency, source radius, stress drop and moment tensor using synthetic events created within elastodynamic numerical modelling software, WAVE3D. The main objective is to determine whether the source parameters calculated from the recorded waveforms are due to a combination of the stope source and the pillar sources, rather than being related only to crushing of the pillar or shearing in the pillar footwall. The main finding is that the presence of stopes, and types of pillars, have a significant impact on the seismic moment and other source parameters. This is important since the moment is viewed as a robust parameter on which seismic magnitude is often based; however, this study indicates that moments calculated for pillar failure in a tabular stoping environments are less representative of the shearing or crushing source than originally thought. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

Theoretical study of the excitation, spectral characteristics, and geometrical attenuation of regional seismic phases

1984 ◽  
Vol 74 (1) ◽  
pp. 79-90
Author(s):  
Michel Campillo ◽  
Michel Bouchon ◽  
Bernard Massinon
Keyword(s):  
Rayleigh Waves ◽  
Wave Amplitude ◽  
Theoretical Study ◽  
Epicentral Distance ◽  
Spectral Characteristics ◽  
Source Depth ◽  
Source Mechanisms ◽  
Lg Wave ◽  
Two Phases

Abstract We present a theoretical study of the generation and geometrical attenuation of regional crustal phases. We do this through the computation of seismograms in the epicentral distance range from 60 to 500 km. The geometrical attenuation of Lg waves with epicentral distance is of the form r−0.83. Pg wave amplitudes display a much stronger decay of the form r−1.5. The spectral density of the crustal transfer function for Pg waves is relatively flat for frequencies between 0.1 and 5 Hz while Lg wave spectra strongly fall off beyond 2 to 3 Hz. The excitation of Pg wave is insensitive to the depth of the source within the crust while the Lg amplitude is about 50 per cent higher for a source in the upper and middle crust than in the lower crust. The amplitudes of these two phases drastically decrease when the source is below the Moho. These results illustrate the important role of wave guide played by the crust for the propagation of Lg and Pg. We find that the geometrical attenuation of Pg and Lg waves is independent of source mechanisms. In the case of an explosion, the excitation of Pg is insensitive to the source depth. The Lg wave amplitude is small in comparison to Pg and Rayleigh waves and depends on the closeness of the source to an interface or to the free surface.

A source theory for complex earthquakes

1975 ◽  
Vol 65 (5) ◽  
pp. 1385-1405 ◽  
Author(s):  
R. R. Blandford
Keyword(s):  
Fault Plane ◽  
Amplitude Ratio ◽  
P Wave ◽  
Corner Frequency ◽  
Transform Faults ◽  
Shallow Earthquakes ◽  
Short Period ◽  
Wave Forms ◽  
The Moment ◽  
Third Moment

Abstract Earthquake source theories of Haskell, Brune, and Savage have been drawn upon to develop a description of an earthquake as a major slip accompanied by many smaller tensional and slip events. We find natural explanations of several previously unexplained observations, such as: Robustness of the MS: mb discriminant, P corner frequency higher than S corner frequency for shallow earthquakes, High-frequency P/S amplitude ratio higher for shallow earthquakes than previous theories predict, Increase of complexity as a function of third moment, Small mb relative to MS for transform faults. (This can also be explained by emergent short-period P wave forms or by a low-Q region underlying the source). The theory predicts that MS:mb populations of earthquakes and explosions will not converge at small magnitudes. The theory also suggests that the standard interpretations of corner-frequency measurements can provide only a lower limit to fault-plane dimensions and, in combination with the moment, only an upper limit on stress drop.

scholarly journals The reaction of cytochrome o in Escherichia coli with oxygen. Low-temperature kinetic and spectral studies

1979 ◽  
Vol 184 (2) ◽  
pp. 379-389 ◽  
Author(s):  
R K Poole ◽  
A J Waring ◽  
B Chance
Keyword(s):  
Escherichia Coli ◽  
Low Temperature ◽  
Flash Photolysis ◽  
Spectral Characteristics ◽  
Spectral Studies ◽  
Oxygen Compound ◽  
Intact Cells ◽  
Lower Velocity ◽  
Cytochrome D ◽  
O2 Binding

1. The reactions of cytochrome omicron in intact cells of aerobically grown Escherichia coli with O2 and CO have been studied at low temperature. 2. Flash photolysis of CO-liganded cells in the presence of O2 and at temperatures between −79 and −102 degrees C results in the oxidation of kinetically heterogeneous beta-type cytochromes (including cytochrome omicron), but not of cytochrome d. 3. The reaction of reduced cytochrome omicron with O2 involves O2 binding to give intermediate(s) with spectral characteristics similar to that of the reduced oxidase-CO complex. Observation in the alpha-region suggests that unexplained ligand dissociation accompanies the initial O2 binding. 4. At temperatures below −98 degrees C, an ‘end point’ in the reaction is reached; further reaction and oxidation of cytochrome omicron occurs on raising the temperature. 5. There is a linear relationship between the rate of formation of the oxygen compound and the O2 concentration up to 0.5 mM. The second-order constant for its formation (k+1) is 0.91 M−1.S−1 at −101 degrees C. The reaction is not readily reversible, the value of k−1 being 1.4 × 10(-5) S−1 and the kd 1.5 × 10(-5) M. 6. The energy of activation for this reaction at low temperatures is 29.9kJ (7.1 kcal)/mol. 7. The reaction with O2 is distinguished from that with CO by the markedly lower velocity and high photolytic reversibility of the latter. 8. Comparisons are drawn between the intermediate(s) in the O2 reaction of cytochrome omicron in E. coli and those identified in other bacteria and in the reaction of cytochrome aa3 with O2.

scholarly journals Conversion between the local magnitude (ML) and the moment magnitude (Mw) for earthquakes in the Croatian Earthquake Catalogue

Geofizika ◽  
2020 ◽  
Vol 37 (2) ◽  
pp. 197-211
Author(s):  
Marijan Herak
Keyword(s):  
Aspect Ratio ◽  
Residual Analysis ◽  
Earthquake Catalogue ◽  
Moment Magnitude ◽  
Coefficient Of Determination ◽  
Local Magnitude ◽  
The Moment ◽  
Best Fit ◽  
Mechanical Seismographs

Based on 153 earthquakes (1959–2020) listed in the Croatian Earthquake Catalogue, a conversion relation was obtained between the local magnitude ML,CR and the corresponding moment magnitude Mw as reported by the global and regional agencies. As errors were present in both variables the York regression was used. The best fit line is given by: MwL = (–0.106 ± 0.122) + (1.002 ± 0.027) ML,CR (coefficient of determination R2 = 0.90). The earthquakes considered occurred in Croatia and the neighbouring regions, and their local magnitudes ML,CR ranged between 3.5 and 6.5. Residual analysis suggests that an artificial positive magnitude shift of up to 0.3 magnitude units may have occurred in the early 1980s, when Wiechert mechanical seismographs were replaced by the instruments with velocity proportional recordings without proper recalibration of the magnitude formula. The slope of the regression close to 1.0 indicates that on the average the faults’ aspect ratio (width/length) is about 1/2.

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